1. Field of the Invention
The present invention relates to a recording apparatus such as a printer, a copying machine, a word processor, a personal computer, a facsimile and the like. More particularly, it relates to a recording apparatus in which a recording sheet is pinched between and conveyed by a pinch roller and a convey roller and, after recording, the recording sheet is pinched between and discharged by a discharge roller and spur wheels.
2. Related Background Art
An example of conventional techniques with reference will be explained to FIG. 13, a pinch roller 5 is always urged against a recording sheet 3 or a convey roller 4. Further, a discharge roller 11 is selected to have a convey amount slightly greater than that of the convey roller 4 so that tension is applied to the recording sheet 3 to eliminate looseness of the recording sheet and permit the recording under a good condition. After the recording sheet 3 leaves the pinch roller 5, the recording sheet is discharged mainly by a conveying force of the discharge roller 11.
However, the above-mentioned conventional technique has the following disadvantages.
(1) When a trail end of the recording sheet 3 leaves the pinch roller 5, as shown in FIG. 4, the recording sheet is subjected to a force F directed toward a downstream direction and a downward direction, so that, since a convey distance of the recording sheet 3 is increased and conveying accuracy is worsened, recording accuracy at a rear end portion of the recording sheet 3 is worsened.
(2) After the trail end of the recording sheet 3 leaves the pinch roller 5, since the recording sheet is conveyed mainly by the discharge roller 11 and spur wheels 12 which are rotated faster than the convey roller 4, a convey distance of the recording sheet 3 per one line space is increased to worsen the conveying accuracy, thereby worsening the recording accuracy at the rear end portion of the recording sheet 3.
To eliminate the above-mentioned conventional drawbacks, the present invention provides a (first) recording apparatus comprising a recording portion for effecting the recording on a recording sheet, a convey means for conveying the recording sheet to the recording portion by pinching the recording sheet between a pinch roller and a convey roller, and a discharge means for discharging the recording sheet by pinching the recording sheet between a spur wheel and a discharge roller. It further comprises an urging means for urging the pinch roller against the recording sheet, an urging force controlling means for controlling an urging force of the urging means, and a detecting means for detecting the fact that a trail end of the recording sheet is conveyed up to a predetermined position disposed upstream of a position where the trail end of the recording sheet leaves the pinch roller, wherein the urging force controlling means reduces the urging force of the urging means on the basis of a detection result from the detecting means.
The present invention further provides a recording apparatus comprising a (second) recording portion for effecting the recording on a recording sheet, a convey means for conveying the recording sheet to the recording portion by pinching the recording sheet between a pinch roller and a convey roller, and a discharge means for discharging the recording sheet by pinching the recording sheet between a spur wheel and discharge roller. It further comprises an urging means for urging the pinch roller against the recording sheet, an urging force controlling means for controlling an urging force of the urging means, and a detecting means for detecting the fact that a trail end of the recording sheet is conveyed up to a predetermined position disposed upstream of a position where the trail end of the recording sheet leaves the pinch roller, wherein the urging force controlling means releases the urging force of the urging means on the basis of a detection result from the detecting means.
The present invention also provides a (third) recording apparatus comprising a recording portion for effecting the recording on a recording sheet, a convey means for conveying the recording sheet to the recording portion by pinching the recording sheet between a pinch roller and a convey roller, and a discharge means for discharging the recording sheet by pinching the recording sheet between a spur wheel and a discharge roller. It further comprises a rotation controlling means for controlling rotations of the convey roller and the discharge roller, and a detecting means for detecting the fact that a trail end of the recording sheet is conveyed up to a predetermined position disposed upstream of a position where the trail end of the recording sheet leaves the pinch roller, wherein the rotation controlling means reduces convey amounts of the convey roller and the discharge roller corresponding to one line space.
The present invention further provides a (fourth) recording apparatus comprising a recording portion for effecting the recording on a recording sheet, a convey means for conveying the recording sheet to the recording portion by pinching the recording sheet between a pinch roller and a convey roller, and a discharge means for discharging the recording sheet by pinching the recording sheet between a spur wheel and a discharge roller. It further comprises a rotation controlling means for controlling rotation of the discharge roller, and a detecting means for detecting the fact that a trail end of the recording sheet is conveyed up to a predetermined position disposed upstream of a position where the trail end of the recording sheet leaves the pinch roller, wherein the rotation controlling means reduces a convey amount of the discharge roller corresponding to one line space.
The first or second recording apparatus may further include a rotation controlling means for controlling rotation of the convey roller and the discharge roller so that the rotation controlling means reduces convey amounts of the convey roller and the discharge roller corresponding to one line space. Alternatively, the first or second recording apparatus may further include a rotation controlling means for controlling rotation of the discharge roller so that the rotation controlling means reduces convey amount of the discharge roller corresponding to one line space.
In the third recording apparatus, the rotation controlling means may set the convey amount of the discharge roller to become the same as a convey amount of the convey roller before detected by the detecting means. In the fourth recording apparatus, the rotation controlling means may set the convey amount of the discharge roller to become the same as a convey amount of the convey roller before detected by the detecting means.
When the first or second recording apparatus includes the rotation controlling means for controlling rotation of the convey roller and the discharge roller, the rotation controlling means may set the convey amount of the discharge roller to become the same as a convey amount of the convey roller before detected by the detecting means. When the first or second recording apparatus includes the rotation controlling means for controlling rotation of the discharge roller, the rotation controlling means may set the convey amount of the discharge roller to become the same as a convey amount of the convey roller before detected by the detecting means.
In any of the first to fourth recording apparatuses, the detection means may comprise a sensor disposed in the vicinity of the convey roller, and a rotation amount measuring means for measuring a rotation amount of the convey roller. In any of the first to fourth recording apparatuses, the recording portion may be of ink jet recording type in which the recording is effected by discharging ink in response to a signal.
In any of the first to fourth recording apparatuses, the recording portion may be of ink jet recording type in which the recording is effected by discharging ink by growth of a bubble formed by heating the ink to exceed the film-boiling temperature generated by energizing an electrical/thermal converter in response to a signal.